This invention relates to a plastic blow molded container having a freestanding base structure for supporting the container while being capable of withstanding internal pressure.
Conventional plastic blow molded containers for holding carbonated beverages that pressurize the container for the most part in the past have been manufactured as base cup containers wherein the lower extremity of the blow molded container has a hemispherical shape that is received within an injection molded plastic base cup which supports the container during use. Such a base cup permits the hemispherical shape to be utilized to provide the requisite strength for withstanding the internal pressure while still providing a flat surface on which the container can be supported in an upright position. While such containers function satisfactorily, there is a cost involved in both manufacturing and assembling the base cup to the blow molded container and such cost must necessarily be included in the price to the consumer.
Blow molded containers capable of withstanding pressure have also been manufactured with freestanding base structures that are unitary with the container body such as disclosed by U.S. Pat. No. 3,598,270 Adomaitis; U.S. Pat. No. 3,727,783 Carmichael; U.S. Pat. No. 3,759,410 Uhilig; U.S. Pat. No. 3,871,541 Adomaitis; and U.S. Pat. No. 3,935,955 Das; and by European Patent Application Publication Number 0 225 155. These patents disclose relatively early attempts to design a freestanding blow molded container capable of withstanding internal pressure by the provision of circumferentially spaced legs having lower feet on which the container is supported.
More recent plastic blow molded containers having freestanding base structures are disclosed by German Offenlegungsschrift 29 20 122 and Japanese patent document No. 1-99949 Sakano dated Apr. 18, 1989; and by U.S. Pat. No. 4,249,667 Pocock et al; U.S. Pat. No. 4,267,144 Collette et al; U.S. Pat. No. 4,276,987 Michel; U.S. Pat. No. 4,294,366 Chang; U.S. Pat. No. 4,318,489 Snyder et al; U.S. Pat. No. 4,335,821 Collette et al; U.S. Pat. No. 4,368,825 Motill; U.S. Pat. No. 4,785,949 Krishnakumar et al; U.S. Pat. No. 4,785,950 Miller et al; U.S. Pat. No. 4,850,493 Howard, Jr.; U.S. Pat. No. 4,850,494 Howard, Jr.; U.S. Pat. No. 4,867,323 Powers; and U.S. Pat. No. 4,910,054 Collette et al; U.S. Pat. No. 4,978,015 Walker; U.S. Pat. No. 4,598,831 Nakamura et al; U.S. Pat. No. 5,024,340 Alberghim et al; U.S. Pat. No. 5,064,080 Young et al; U.S. Pat. No. 5,072,841 Okhai; U.S. Pat. No. 5,133,468 Brunson et al; and U.S. Pat. No. 5,139,162 Young et al.
Also, U.S. Pat. No. 4,785,949 Krishnakumar et al and Japanese patent document No. 4-44943 Takakusaki disclose plastic blow molded containers having freestanding base structures including feet that is separated by curved ribs that taper from wider outer upper ends to narrower inner lower ends.
Certain of the containers disclosed by the above patents have flat feet on which the freestanding base structure is supported. However, some of the structures involved deflect under the pressure such that it is necessary to incline the lower feet upwardly in an inward direction as disclosed by U.S. Pat. No. 4,865,206 Behm et al so that the feet deflect downwardly to a coplanar relationship with each other upon being subjected to the internal pressure when the container is filled.
Also, United Kingdom patent application GB2189214A discloses a plastic blow molded container having a unitary base structure with a recess defined by a peripheral wall and a convex bottom wall. This recess is disclosed as functioning to centralize the preform used to blow mold the container and to also prevent the lower gate area through which the preform is injection molded from becoming the lowest portion of the container in a manner that could adversely affect stability.
An object of the present invention is to provide an improved plastic blow molded container having a freestanding base structure that provides good stability to the container even when subjected to internal pressure.
In carrying out the above object, the plastic blow molded container incorporating the invention has a central axis A and includes a cylindrical body portion that extends vertically about the central axis A with a diameter D. An upper end closure of the container is unitary with the upper extremity of the cylindrical body portion and includes a dispensing spout through which the container is filled and through which the container contents are subsequently dispensed as needed. A freestanding base structure of the container is unitary with the cylindrical body portion to close the lower extremity thereof and is constructed in accordance with the present invention.
The freestanding base structure of the invention includes a plurality of downwardly projecting hollow legs spaced circumferentially from each other with respect to the body portion. Each leg has a lower flat foot coplanar with the feet of the other legs to cooperate therewith in supporting the container in an upright position. Each leg also has an outer wall that extends from the outer extremity of the flat foot thereof to the cylindrical body portion. The flat foot and the outer wall of each leg have a curved junction. Each leg also has a inner connecting portion that is inclined and extends upwardly and inwardly from the inner extremity of its flat foot. A pair of side walls of each leg cooperate with the flat foot, the outer wall and the planar inner connecting portion thereof to close the leg.
The freestanding base structure of the container also includes a plurality of curved ribs spaced circumferentially from each other between the downwardly projecting legs and connecting the adjacent side walls of the legs. Each rib has an outer upper end that has a circumferential width Wu and extends upwardly for connection to the cylindrical body portion of the container. Each rib also has an inner lower end located between the inner connecting portions of the legs on opposite sides of the legs and extending downwardly and inwardly toward the central axis A of the container. The inner lower end of each rib has a circumferential width Wl that is larger than the circumferential width Wu of the outer upper end of the rib. Each rib also has a curved intermediate portion that extends between the outer upper and inner lower ends thereof with an outwardly convex shape.
A generally round hub of the freestanding base structure of the container is located along the central axis A with the legs and the curved ribs of the base structure extending radially in an outward direction from the hub. This hub has a diameter Dh in the range of about 0.15 to 0.25 of the diameter D of the cylindrical body portion. The hub also has connections to the upwardly extending inner connecting portions of the legs and the hub also has connection to the downwardly extending inner lower ends of the curved ribs.
The freestanding base structure of the plastic blow molded container has a construction that is capable of withstanding internal pressure after filling.
In one preferred embodiment, the hub has an upwardly extending shape and includes a periphery connected to the upwardly extending inner connecting portions of the legs and to the downwardly extending inner lower ends of the curved ribs.
In another preferred embodiment of the plastic blow molded container, the hub of the freestanding base structure has a generally flat shape that extends horizontally and includes a periphery connected to the upwardly extending inner connecting portions of the legs and to the downwardly extending inner lower ends of the curved ribs.
In a further embodiment of the plastic blow molded container, the hub of the freestanding base structure has a downwardly extending shape including a periphery connected to the inwardly extending inner connecting portions of the legs and to the downwardly extending inner lower ends of the curved ribs.
Each embodiment of the plastic blow molded container also has the lower flat feet thereof provided with an outer diameter Df and has a periphery of the hub spaced above the plane of the flat feet of the legs by a height Hp, and the ratio of the diameter Df over the height Hp is in the range of about 25 to 90.
Each embodiment of the plastic blow molded container has the cylindrical body portion provided with a nominal wall thickness t and has the inner extremities of the flat feet, the planar inner connecting portions of the legs, the inner lower ends of the curved ribs and the hub each provided with a wall thickness txe2x80x2 that is at least 1.7 times the nominal wall thickness t of the cylindrical body portion.
Each embodiment of the plastic blow molded container further has the lower flat foot of each leg provided with a truncated wedge shape and each curved rib has a generally flat cross section between its ends. The outer wall of each leg has a curved shape including an upper end that is tangent with the adjacent portion of the lower extremity of the cylindrical body portion. This outer wall of each leg has a radius of curvature Rw greater than 0.75 of the diameter D of the cylindrical body portion. Each rib of the preferred construction of the container has a radius of curvature Rr greater than about 0.6 of the diameter D of the cylindrical body portion and has a center of curvature on the opposite side of the central axis A from the rib.
The preferred construction of each embodiment of the plastic blow molded container is disclosed as including an odd number of legs and ribs with each leg located in a diametrically opposite relationship to an associated rib. Five legs and five ribs make up the freestanding base structure of each disclosed embodiment with each leg being located diametrically opposite an associated rib and with the legs and ribs extending radially from the hub in a circumferentially alternating relationship.